This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | -1 |
| 2 | -1 |
| 3 | 2 |
| 4 | 1 |
| 5 | 9 |
| 6 | 1 |
| 7 | 146 |
| 8 | -167 |
| 9 | 5363 |
| 10 | -16109 |
| 11 | 355354 |
| 12 | -1844831 |
| 13 | 37142117 |
| 14 | -279336147 |
| 15 | 5615638874 |
| 16 | -55537087439 |
| 17 | 1157104637831 |
| 18 | -14174652825017 |
| 19 | 311217052899986 |
| 20 | -4538156701549279 |
| 21 | 105770066665097729 |
| 22 | -1785320722016719271 |
| 23 | 44287095132343348482 |